A conventional hub motor is disclosed in U.S. Pat. No. 6,321,863 and includes an electrical motor received in a hub which is driven by the electrical motor. Nevertheless, the lack of better speed changing system for the conventional hub motor, electrical motor wastes too much electric power and the efficiency of the rotation of the hub is not satisfied. Some alternative inventions for the hub motors are disclosed in U.S. Pat. No. 4,294,138 and 5,273,500. Although a planetary gear system is used in these inventions, the lack of the use of electrical motor makes the hub be inconvenient in practical use.
The present invention intends to provide a hub assembly which is driven by an electrical motor. A planetary gear system is connected with the electrical motor so as to smoothly and efficiently rotate the hub.